This invention relates to a method for preparing a luminescent viewing screen comprising a light-absorbing matrix on a support; and particularly to a method wherein the supports which have defective in-process screens thereon can be recycled without disturbing the matrix.
Some prior color-television picture tubes include a light-absorbing matrix as a structural part of the luminescent viewing screen. In such tubes, a light-absorbing matrix is supported on the inner surface of the faceplate panel of the tube. The matrix has a multiplicity of openings therein, which may be in the shape of dots or lines, with phosphor filling each opening in the matrix, and with a specular metal layer over the phosphor.
In one sequence of fabrication processes commonly used in the picture-tube industry, the matrix is prepared by reverse printing, as described, for example, in U.S. Pat. Nos. 3,558,310 to E. E. Mayaud and 4,049,452 to E. E. Nekut. After such a matrix is deposited on the inner surface of a panel, a patterned layer of phosphor particles is deposited photographically on the matrix. The phosphor-particle layer is dried and then coated with a film of organic polymeric material as described, for example, in U.S. Pat. Nos. 3,582,389 and 3,582,390, both to T. A. Saulnier. The film is then metallized, usually by vapor depositing aluminum metal thereon.
During the fabrication processes following the deposition of the matrix, some screens are found to be defective. By the prior salvaging method, the entire structure, including the matrix, is stripped from the panel of the tube, and a new screen structure is produced on the salvaged panel. In most cases, the matrix is not defective, and considerable savings can be realized if the matrix can be salvaged with the panel. Attempts have been made to remove the material overlying the matrix by contacting the matrix with oxidizing solutions which are used to develop a matrix. Examples of such oxidizing solutions are disclosed in the Mayaud and Nekut patents cited above. Although most of the overlying material was removed with oxidizing solutions, nevertheless enough material remained to consider the panel and matrix unacceptable for recycling.